1. Field
This disclosure is related to interfacing between a device and a host computing platform or system.
2. Background
Two significant challenges that face the computing industry as technology continues to advance are power consumption issues and thermal issues. These issues or challenges are particularly acute in mobile applications in which the platform in more constrained in terms of the amount of power available and/or its capability to handle significant amounts of heat than are some other platforms, such as, for example, a desktop platform. At the same time, computing industry technology is heading in a direction in which high speed serial buses are becoming more desirable. One example of a data transport for this purpose currently gaining industry attention is the IEEE 1394 specification, “IEEE Standard for a High Performance Serial Bus,” IEEE Std 1394-1995, 30 Aug. 1996, available from the Institute of Electrical and Electronic Engineers (IEEE), (hereinafter referred to as “1394” or “the 1394 specification”). However, a power consumption and thermal “wall” is expected to arise from the application of 1394 within a power constrained platform, such as, for example, a notebook personal computer (PC) or the like. Of course, although 1394 is discussed here, it is just one example and many other buses employing data transports may have similar issues. Nonetheless, unlike some alternative mobile oriented buses, a 1394 specification compliant interface is a “long haul” data transport intended to drive signals over relatively long distances, such as on the order of meters. This contrasts with a “short haul” interface, which is typically designed to drive intra-chassis signal lines less than 18 inches in length, for example. Therefore, a 1394 specification compliant interface consumes a significant amount of power, and even when not performing signaling. For example, a three port S400-speed physical protocol layer (or “PHY”) integrated circuit (IC) consumes about 0.7 watts and an associated host interface link layer IC may add another 0.4 watts. A single 1394 specification compliant point-to-point connection employs two such interfaces. A three port S-800 PHY (operating at 800 megabits per second) is expected to consume about 1.7 watts, with the supporting link adding about 0.7 watts (i.e., 2.4 watts total per S-800 interface). Furthermore, this power is dissipated as heat, which would be undesirable for a thermally constrained platform. Therefore, unfortunately, using 1394 as just one example, these trends appear inconsistent with or present challenges to the application of a long haul data transport to power and thermally constrained platforms. A need, therefore, exists for an approach to address these power and thermal issues so that a long haul data transport, such as the 1394, may be employed even with power and thermally constrained platforms, such as exist in mobile applications, for example.